United States Patent Application No. 2006/0175837 A1 discloses various embodiments of a pipe clamp having a gasketed center rib that can be used to clamp and seal a pair of ribbed pipe ends. One of the disclosed pipe clamp embodiments (FIGS. 1-4) is in the form of a one-bolt band clamp that can be used for telescopic pipe connections in which one pipe end fits into the other pipe end in an overlapping configuration. Such telescopic connections of the pipe ends are also referred to as a lap joint. These band clamps often can use only a single bolt, with the clamping force from tightening of the bolt being transferred by the clamp to the outer pipe end and through that to the inner pipe end, resulting in sufficient clamping pressure to provide a gas-tight seal of the two pipe ends.
Another of the disclosed embodiments (FIGS. 5-11) from US 2006/0175837 A1 is a two-bolt pipe coupler in which the pipe ends are connected in an abutted end-to-end configuration with no overlapping of the ends. Pipe couplers used in these abutting types of pipe connections typically have a longer axial length so that there is sufficient clamp-to-pipe connection for each of the two pipes. Consequently, these pipe couplers normally use at least two bolts so that sufficient clamping force is applied to each of the two pipe ends. This helps protect against bending moments that might be applied to the clamped joint during installation or when in service. Such bending moments involve a force being applied to the clamped joint that attempts to move one or more of the components (pipes and clamp) in a manner that would tend to cause their axes come out of alignment with each other. Where a clamped joint does not have sufficient stiffness, these bending moments can be responsible for a loss of a gas-tightness at the joint which, for automotive exhaust and various other applications, can be undesirable.
In a lap joint, the telescopic connection of the two pipe ends helps protect against the effects of bending moments on the joint by keeping the two pipe ends generally aligned. However, the pipe end connection can still be adversely affected by these bending moments and this can be for various reasons, including differences in outer diameter of the inner pipe versus the inner diameter of the outer pipe which may present a loose interconnection of the two pipes that permits a small angle to exist between the two pipes' axes. These differences in diameter are common as they may nominally be introduced into the design of the pipe ends to accommodate manufacturing tolerances. And while the clamping pressure from the band clamp helps stiffen the joint, it is nonetheless applied at a single axial location. Thus, in single-bolt designs such as shown in the above-noted published application, the clamping pressure is applied primarily via the clamp's gasket. For some applications, this provides a suitable seal at the joint; however, for certain other applications, it may be desirable to achieve a stiffer connection that provides additional sealing resistance to bending moments.